Human Influence on Climate Change

Climate deals with the weather in some location averaged over some long period of time. Climate of a certain region depends on various factors. A change or alteration in those factors either naturally or by human means ensue a great change in climate bringing out the climate change like shifting in rain fall pattern, temperature pattern etc.

Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors that include oceanic processes (such as oceanic circulation), biotic processes, variations in solar radiation received by Earth, plate tectonics and volcanic eruptions, and human-induced alterations of the natural world; these latter effects are currently causing global warming, and "climate change" is often used to describe human-specific impacts.

Climate change has long-since ceased to be a scientific curiosity, and is no longer just one of many environmental and regulatory concerns. It is the major, overriding environmental issue of our time, and the single greatest challenge facing environmental regulators. It is a growing crisis with economic, health and safety, food production, security, and other dimensions.

Shifting weather patterns, for example, threaten food production through increased unpredictability of precipitation, rising sea levels contaminate coastal freshwater reserves and increase the risk of catastrophic flooding, and a warming atmosphere aids the pole-ward spread of pests and diseases once limited to the tropics.

Agriculture is the basic activity by which humans live and survive on the earth. Assessing the impacts of climate change on agriculture is a vital task. In both developed and developing countries, the influence of climate on crops and livestock persists despite irrigation, improved plant and animal hybrids and the growing use of chemical fertilizers. The continued dependence of agricultural production on light, heat, water and other climatic factors, the dependence of much of the world's population on agricultural activities, and the significant magnitude and rapid rates of possible climate changes all combine to create the need for a comprehensive consideration of the potential impacts of climate on global agriculture.

Change in climatic variables has further aggravated the situation over time. In Nepal, climate related changes are observed in precipitation patterns, temperature, high intensity floods, landslides, soil erosion and increased sedimentation. The average warming in annual temperature in Himalayan and its vicinity between 1997 and 1994 was 0.06◦c per year and 0.04◦c in the terai region (Shrestha et al. 1999). The change through the livelihood of local countries that changes in agroecosystem and direct threats such as loss of land, livestock and households assets. Some farmers are observed taking different adaptations measure such as changing the agricultural calendar, changing the cropping patterns resorting to alternate sources of irrigation, etc. while increasing attention has been placed on glacial lake outburst floods in Nepal, little attention has been given to other effects of climate change including the agricultural crops.

There is alarming evidence that important tipping points, leading to irreversible changes in major ecosystems and the planetary climate system, may already have been reached or passed. Ecosystems as diverse as the Amazon rainforest and the Arctic tundra, for example, may be approaching thresholds of dramatic change through warming and drying. Mountain glaciers are in alarming retreat and the downstream effects of reduced water supply in the driest months will have repercussions that transcend generations. Climate feedback systems and environmental cumulative effects are building across Earth systems demonstrating behaviours we cannot anticipate.

Growing body of literature suggests that climate change will significantly affect agriculture sector in developing countries and this may have serious consequences on the level of food production and food security and would adversely affect huge population, with larger impacts on poor and small holder farmers, especially in developing countries. having recognize the potential impacts of climate change as long term threat to agriculture sector bulk of impacts study are available for developed countries while little is known about potential impacts in developing countries.

Factors responsible for the Climate Change

The earth's climate is dynamic and always changing through a natural cycle. The causes of climate change can be divided into two categories - those that are due to natural causes and those that are created by man. These causes are listed below:

1.               Natural causes

·                  Continental drift

·                  Volcanoes

·                  The earth’s tilt

·                  Ocean currents

2.               Human causes

·            Increase in greenhouse gases

·            Increase in aerosols

It is extremely likely that human activities are by far the dominant cause of climate change. The primary such human factor was increasing greenhouse gas concentrations due to fossil fuel burning and other human activities. A secondary human factor, sulphate aerosols emitted from industrial smokestacks, also played a role, however. Like volcanic sulphate aerosols, these industrial aerosols have a cooling effect. Unlike volcanic aerosols, which reach the lower stratosphere, allowing them to spread out into a layer covering the globe, industrial aerosols remain confined to the lower atmosphere, leading to localized patterns of cooling that offset global warming in some regions.

Aerosols influence the global radiation budget and so changes in the atmospheric aerosol load due to either natural causes or human activity will contribute to climate change. A large fraction of the mass of tropospheric aerosol is wind-blown mineral dust (Tegen and Lacis, 1996). Human activity increases the atmospheric water vapour content in an indirect way through climate feedbacks. We conclude here that human activity also has a direct influence on the water vapour concentration through irrigation (Boucher et al. 2004). The calculations suggest that all of the complex range of effects of the human disturbance of climate need to be considered in order to understand the human influence on climate, rather than focusing on a subset of the human disturbances (RA Pielke, 2005).

Human  activities  contribute  to  climate  change  by  causing changes in Earth’s atmosphere in the amounts of greenhouse gases,  aerosols  (small  particles),  and  cloudiness.  The largest known contribution comes from the burning of fossil fuels, which releases carbon dioxide gas to the atmosphere. Greenhouse gases and aero-sols  affect  climate  by  altering  incoming  solar  radiation  and  out-going infrared (thermal) radiation that are part of Earth’s energy balance. Changing the atmospheric abundance or properties of these gases and particles can lead to a warming or cooling of the climate system. Since the start of the industrial era (about 1750), the overall effect of human activities on climate has been a warming influence. The human impact on climate during this era greatly exceeds that due to known changes in natural processes, such as solar changes and volcanic eruptions.

Human activities impacting on climate

Some of the human activities contributing climate change and affecting climates and their global and local effects are:-

Activity	Climatic effect	Scale and importance of the effect
Release of carbon dioxide by burning fossil fuels	Increases the atmospheric absorption and emission of terrestrial infrared radiation (greenhouse effect), resulting in warming of lower atmosphere and cooling of the stratosphere.	Global: potentially a major influence on climate and biological activity.
Release of chlorofluoromethanes, nitrous oxide, carbon tetrachloride, carbon disulfide	Similar climatic effect as that of carbon dioxide since these, too, are infrared-absorbing and fairly chemically stable trace gases.	Global: potentially significant influence on climate.
Release of particles (aerosols) from industrial and agricultural practices	These sunlight scattering and absorbing particles probably decrease albedo over land, causing a warming and could increase albedo over water, causing a cooling; they also change stability of lower atmosphere; net climatic effects still speculative.	Largely regional, since aerosols have an average lifetime of only a few days, but similar regional effects in different parts of the world could have non negligible net global effects; stability increase may suppress convective rainfall, but particles could affect cloud properties with more far-reaching effects.
Release of aerosols that act as condensation and freezing nuclei	Influences growth of cloud droplets and ice crystals; may affect amount of precipitation or albedo of clouds in either direction.	Local (at most) regional influences on quantity and quality of precipitation, but unknown and potentially important change to earth's heat balance if cloud albedo is altered.
Release of heat (thermal pollution)	Warms the lower atmosphere directly.	Locally important now; could become significant regionally; could modify large-scale circulation.
Upward transport of chlorofluoromethanes and nitrous oxide into the stratosphere	Photochemical reaction of their dissociation products probably reduces stratospheric ozone.	Global but uncertain influence on climate: less total stratospheric ozone probably allows more solar radiation to reach the surface but compensates by reducing greenhouse effect as well; however, if ozone concentration decreases at high altitudes, but increases comparably at lower altitudes, this would lead to potentially very large surface warming; could cause significant biological effects from increased exposure to ultraviolet radiation if total column amount of ozone decreases.
Release of trace gases (e.g., nitrogen oxides, carbon monoxide, or methane) that increase tropospheric ozone by photochemical reactions	Large atmospheric heating occurs from tropospheric ozone, which enhances both solar and greenhouse heating of lower atmosphere.	Local to regional at present, but could become a significant global climatic warming if large-scale fossil fuel use leads to combustion products that significantly increase tropospheric ozone levels; contact with ozone also harms some plants and people.
Patterns of land use, e.g., urbanization, agriculture, overgrazing, deforestation etc	Changes surface albedo and evapotranspiration and causes aerosols.	Largely regional: net global climatic importance still speculative.
Release of radioactive Krypton-85 from nuclear reactors and fuel reprocessing plants	Increases conductivity of lower atmosphere, with possible implications for earth's electric field and precipitation from convective clouds.	Global: importance of influence is highly speculative.
Large-scale nuclear war.	Could lead to very large injections of soot and dust causing transient cooling lasting from weeks to months, depending on the nature of the exchange and on how many fires were started.	Could be global, but initially in mid-latitudes of Northern Hemisphere. Darkness from dust and smoke could wipe out photosynthesis for weeks with severe effects on both natural and agricultural ecosystems of both combatant and noncombatant nations. Transient freezing outbreaks could eliminate most warm season crops in mid-latitudes or be devastating to any vegetation in tropics or subtropics.

Table — Summary of Principal Human Activities That Can Influence Climate Change (source: Schneider, S.H. and R. Londer, 1984).

Greenhouse effect and global warming

An increasing body of observations gives a collective picture of a warming world and other changes in the climate system... There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities (IPCC, 2007).

The global average surface temperature has raised 0.6 ± 0.2 °C since the late 19th century, and 0.17 °C per decade in the last 30 years. There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities, in particular emissions of the greenhouse gases carbon dioxide and methane (IPCC Working Group I on global warming, 2007).

If greenhouse gas emissions continue the warming will also continue, with temperatures projected to increase by 1.4 °C to 5.8 °C between 1990 and 2100. Accompanying this temperature increase will be increases in some types of extreme weather and a projected sea level rise. From IPCC Working Group II: On balance the impacts of global warming will be significantly negative, especially for larger values of warming. (IPCC, 2007)

Figure 2: Figure 2: Patterns of concentration of CO2 and other greenhouse gases throughout many years

Human  activities  result  in  emissions  of  four  principal  green-house  gases:  carbon  dioxide  (CO2),  methane  (CH4),  nitrous  oxide (N2O) and the halocarbons (a group of gases containing fluorine, chlorine and bromine). These gases accumulate in the atmosphere, causing concentrations to increase with time. Significant increases in all of these gases have occurred in the industrial era. All of these increases are attributable to human activities causing many serious problems as a consequence of greenhouse effect.

Greenhouse effect is warming that result when the atmosphere traps heat radiating from Earth toward space (IPCC Fourth Assessment Report, 2007)

THE INFLUENCE OF CLIMATE CHANGE ON CROP PRODUCTION

At the basis of any understanding of climate impacts on agriculture lie the biophysical sciences. The rates of most biophysical processes are highly dependent on climate variables such as radiation, temperature, and moisture that vary regionally. For example, rates of plant photosynthesis depend on the amount of photosynthetically active radiation and levels of atmospheric carbon dioxide (C02). Temperature is an important determinant of the rate at which a plant progresses through various phenological stages towards maturity. The accumulation of biomass is constrained by the availability of moisture and nutrients to a growing plant.

Numerous studies have examined the impacts of past climatic variations on agriculture using case studies, statistical analyses and simulation models (e.g. Nix 1985; Parry 1978; Thompson 1975; World Meteorological Organization 1979). Such studies have clearly demonstrated the sensitivity of both temperate and tropical agricultural systems and nations to climatic variations and changes. In the temperate regions, the impacts of climate variability, particularly drought, on yields of grains in North America and the Soviet Union have been of particular concern because of their effects on world food security. In the tropics, drought impacts on agriculture and resulting food shortages have been widely studied, especially when associated with the failure of the monsoon in Asia or the rains in Sudano-Sahelian Africa. In the temperate regions, climatic variations are associated with economic disruptions; in the tropics, droughts bring famine and widespread social unrest (Pierce 1990).

Major Climatic Changes directly affecting agriculture:

    a. Rising sea level decreases coastal land.  This is problematic because the majority of the world's population resides on our near the coast. Furthermore, the majority of the world's population is located in LDCs in increasingly greater proportions as total world population grows.

    b. Shifting rainfall patterns will change the growing locations of various crops. Some regions will be better suited for agriculture, while others will experience decreased yields.

    c. Shifting temperature ranges will affect changes in the lengths of growing seasons.  Farmers will need to adjust planting and harvesting dates.

Indirect climatic effects on agriculture

In qualitative terms, many indirect effects of climate change on agriculture can be conjectured. Most of them are estimated to be negative and they catch most of the attention of the media. These effects include:

·         The overall predictability of weather and climate would decrease, making the day-to-day and medium-term planning of farm operations more difficult;

·         Loss of biodiversity from some of the most fragile environments, such as tropical forests and mangroves;

·         sea-level rise (40 cm in the coming 100 years) would submerge some valuable coastal agricultural land;

·         the incidence of diseases and pests, especially alien ones, could increase;

·         present (agro) ecological zones could shift in some cases over hundreds of kilometres horizontally, and hundreds of metres altitudinally, with the hazard that some plants, especially trees, and animal species cannot follow in time, and that farming systems cannot adjust themselves in time;

·         higher temperatures would allow seasonally longer plant growth and crop growing in cool and mountainous areas, allowing in some cases increased cropping and production. In contrast, in already warm areas climate change can cause reduced productivity;

·         The current imbalance of food production between cool and temperate regions and tropical and subtropical regions could worsen.

·         there are damaging effects of increasing UV-B on crops, animals and plankton growth. It has been reported that UV-B affects the ability of plankton organisms to control their vertical movements and to adjust to light levels;

·         reductions in yield of up to 10% have been measured at experimentally very high UV-B values, and would be particularly effective in plants where the CO₂ fertilization effect is strongest. On the other hand, UV-B increase could increase the amount of plant internal compounds that act against pests.

·         rising temperatures - now estimated to be 0.2°C per decade, or 1 °C by 2040 (Mitchell et al., 1995) with smallest increases in the tropics (IPCC, 1992) - would diminish the yields of some crops, especially if night temperatures are increased (the temperature increase since the mid-1940s is mainly due to increasing night-time temperatures, while CO₂-induced warming would result in an almost equally large rise in minimum and maximum temperatures (Kukla and Karl, 1993);

·         higher temperatures could have a positive effect on growth of plants of the CAM type. They would also strengthen the CO₂ fertilization effect and the CO₂ anti-transpirant effect of C₃ and C₄ plants unless plants get overheated;

·         higher night temperature may increase dark respiration of plants, diminishing net biomass production;

·         Higher cold-season temperatures may lead to earlier ripening of annual crops, diminishing yield per crop, but would allow locally for the growth of more crops per year due to lengthening of the growing season. Winter kill of pests is likely to be reduced at high latitudes, resulting in greater crop losses and higher need for pest control;

·         higher temperatures will allow for more plant growth at high latitudes and altitudes.

·         the extra precipitation on land, if indeed including present subhumid to semi-arid areas, will increase plant growth in these areas, leading to an improved protection of the land surface and increased rainfed agricultural production; in already humid areas the extra rainfall may, however, impair adequate crop drying and storage;

·         the extra precipitation predicted to occur in some regions provides possibilities for off-site extra storage in rivers, lakes and artificial reservoirs (on-farm or at subcatchment level) for the benefit of improved rural water supply and expanded or more intensive irrigated agriculture and inland fisheries:

·         The effects on water resources and water apportioning of international river and lake basins can be very substantial, with political overtones.

·         The CO₂ fertilization effect: - Higher concentrations of atmospheric CO₂ due to increased use of fossil fuels, deforestation and biomass burning, can have a positive influence on photosynthesis  under optimal growing conditions of light, temperature, nutrient and moisture supply, biomass production can increase, especially of plants with C3 photo-synthetic metabolism , above and even more below ground (Allen et al.). A total of 10 to 20% of the approximate doubling of crop productivity over the past 100 years could be due to this effect (Tans et al., 1990) and forest growth or regrowth may have been stimulated as well

·         The CO₂ anti-transpirant effect: - With increased atmospheric CO₂ the consumptive use of water becomes more efficient because of reduced transpiration. This is induced by a contraction of plant stomata and/or a decrease in the number of stomata per unit leaf area. This restricts the escape of water vapour from the leaf more than it restricts photosynthesis (Wolfe and Erickson, 1993)

Current scenario of climate change effect in the world (Nelson et al, 2009)

o   In developing countries, climate change will cause yield declines for the most important crops. South Asia will be particularly hard hit.

o   Climate change will have varying effects on irrigated yields across regions, but irrigated yields for all crops in South Asia will experience large declines.

o   Climate change will result in additional price increases for the most important agricultural crops–rice, wheat, maize, and soybeans. Higher feed prices will result in higher meat prices. As a result, climate change will reduce the growth in meat consumption slightly and cause a more substantial fall in cereals consumption.

o   Calorie availability in 2050 will not only be lower than in the no–climate-change scenario—it will actually decline relative to 2000 levels throughout the developing world.

o   By 2050, the decline in calorie availability will increase child malnutrition by 20 percent relative to a world with no climate change. Climate change will eliminate much of the improvement in child malnourishment levels that would occur with no climate change.

o   In most developing countries, crop productivity would diminish (some 10% reduction in cereals), which could raise agricultural prices on local and world markets and increase the need for cereal imports, although the global food supply/demand ratio might change only little.

Conclusion

            Climate being overall weather condition of a location averaged over some long period of time, is a totality based on various indices grouped as thermo-agrometerological indices, moisture agrometerological indices and aero dynamics agrometerological indices. A change of alteration in those factors results the climate change. Climate change can occur due to many reasons and causes. The causes may be natural or caused by human beings. It is extremely likely that human activities are by far the dominant cause of climate change. The primary such human factor was increasing greenhouse gas concentrations due to fossil fuel burning and other human activities. A secondary human factor, sulphate aerosols emitted from industrial smokestacks. All of these ultimately result to the climate change. Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., more or fewer extreme weather events). Greenhouse gases and aero-sols  affect  climate  by  altering  incoming  solar  radiation  and  out-going infrared (thermal) radiation that are part of Earth’s energy balance. Changing the atmospheric abundance or properties of these gases and particles can lead to a warming or cooling of the climate system. Different human activities induce the climate changing factors resulting global warming, rise in sea level, shift in temperature pattern, shift in seasonal pattern etc.

            These change in climate impacts on the agriculture locally and globally. Locally it affects the planting season due to the shift in the pattern of the climate, variations in the rainfall, temperature which affects the crops a lot by providing them adverse condition in flowering fruiting stages. The affects are also severe in the global stage, it being produced as a major threat in this 21^st century. Rising sea level decreases coastal land. Shifting rainfall patterns will change the growing locations of various crops. Shifting temperature ranges will affect changes in the lengths of growing seasons.  Farmers will need to adjust planting and harvesting dates.

The change through the livelihood of local countries that changes in agro ecosystem and direct threats such as loss of land, livestock and households assets. Some farmers are observed taking different adaptations measure such as changing the agricultural calendar, changing the cropping patterns resorting to alternate sources of irrigation, etc. while increasing attention has been placed on glacial lake outburst.

            Various steps has to be taken under consideration and implications for the minimization of loss due to this threat and being well prepared for the risks and uncertainties.